174 BOTANICAL GAZETTE [MARCH 
winter in the open under natural conditions, on which occurred 
perithecia in such a stage of development as to expel ascospores 
within two days after being brought into the laboratory. It was 
found that spore expulsion was very slow and limited or did not 
occur at all when the leaves were kept too moist or when main- 
tained in a saturated atmosphere, such as occurs when they are 
placed on moistened filter or blotting paper in a closed Petri dish. 
When the lid of the dish is removed, however, and the leaves are 
alternately allowed to become dry and again moistened by adding 
water to the filter paper beneath them, the spores are expelled in 
considerable quantities. If they are then caught on a glass slide, 
either dry or coated with a thin film of egg albumin, glycerine, or 
some such adhesive, it is found that the spores are deposited in 
clusters or groups of eight. Later, as a very large number of 
spores are discharged from a single ostiole, this grouping of course 
is not apparent. The best method for catching the expelled spores 
was that used by ANDERSON and RANKIN (1) in working with 
Endothia parasitica, as described previously. The glass slide was 
suspended by means of match sticks fastened to it near the ends, 
thus bringing it 3 or 4 mm. above the opening of the ostiole. | 
KLEBAHN (27) has shown that this method of spore expulsion is 
general to Gnomonia and to many other fungi which have Gnomonia- 
like, beaked ostioles. The expulsion of the asci into the neck of 
the ostiole appears largely due to the swelling pressure of the ascus. 
When dry, the ascus with its contained spores occupies considerably 
smaller space than after it has been moistened with water. . Many 
workers have maintained that ascospores are ordinarily liberated 
one at a time, and such may be the case here, since I have been 
unable to, observe the actual act of expulsion of the spores from 
the ascus, but the clusters of the spores intercepted on a glass 
slide suspended above the opening of the ostiole are always in 
groups of eight, and give the impression of having been. expelled 
in a group, as was found by ANDERSON and RANKIN to occur in 
Endothia parasitica. 
Many attempts have been made to germinate the ascospores of 
- Gnomonia ulmea under various conditions, and on a number of 
different nutrient media, ranging from distilled water, tap water, 
